Reinsurer Swiss Re has agreed to pay $6.8bn (£4bn) for the insurance unit of industrial giant General Electric.
The Swiss Re building is one of London's most recognisable
Swiss Re will sell $7.5bn of new shares to finance the acquisition and cover the debts of GE Insurance Solutions.
Buying the firm will turn Swiss Re into the world's largest reinsurance company at a time when premiums are set to rise following problems such as hurricanes.
Analysts say the sale will allow General Electric (GE) to focus on quicker growing areas of business.
"Insurance Solutions has been a tough strategic fit for GE," said company chairman and chief executive Jeff Immelt.
"Over the last five years, the Insurance Solutions business has lost $700m and required the infusion of $3.2bn of capital."
GE, the world's largest company by market value, has been cutting its insurance operations and already has sold units to firms including Warren Buffett's Berkshire Hathaway.
Unsurprisingly, Swiss Re's chief executive John Coomber was more flattering about the company he was buying, saying Insurance Solutions was a "powerful business fit offering tremendous opportunities to strengthen our franchise".
The company is based in Kansas City, Missouri, and had net premiums of $6.2bn last year. At the end of June, the it had assets worth a total of $41.5bn.